Luminair



M. EXELMANS Oct. 9, 1934.

LUMINAIR 3 SheetsSheet 1 Filed NOV. '7, 1931 f I a INVENTOR ATTORNEY M. EXELMANS LUMINAIR Filed Nov. 7, 1931 3 Sheets-Sheet 2 INVENTOR ATTORNEY Oct. 9, 1934. M, EXELMANS 1,976,163

LUMINAIR Filed Nov. 7, 1931 5 Sheets-Sheet 3 INVENTOR W 44 ATTORNEY I 55 ridian curve.

Patented Oct. 9, 1934 PATENT OFFICE 1,976,163 LUMINAIR Maurice Exelmans, Paris, France, assignor to Holophane Company, Inc., New York, N. Y., a corporation of Delaware Application November '7, 1931, Serial No. 573,535 In France November 21, 1930 4 Claims.

employing, on the different portions of the surface, prisms of different angles. Reflecting glassware for mirrored glass is manufactured in molds and the molds are provided with prisms or flutes which are produced on the surface of the reflector. It appears to be much simpler and less costly to construct such molds for symmetric reflectors than for the asymmetric reflectors which would be necessary to obtain analogous distributions. The invention, therefore, simplifies a great deal the manufacture of the reflectors and the necessary details therefor.

The accompanying drawings show, for purposes of illustrating the present invention, sev eral embodiments in which the invention may take form, it being understood that the drawings are illustrative of the invention rather than limiting the same. In these drawings:

' Fig. 1 shows a vertical section of a reflector according to the invention constructed for the purpose of producing parallel beams and for the purpose of comparison with a reflector of the usual type;

Fig. 2 is a plan View of a reflector made according to the present invention giving an asymmetric 5 distribution of light around its axis;

Figs. 3, 4, and 5 are vertical sections on lines 33, 4-4, and 55 of Fig. 2;

Fig. 6 shows a diagrammatic distribution of light of this reflector;

Fig. '7 is a vertical section of a reflector for show windows with a surface of revolution;

Figs. 8 and 9 show a distribution of light to be obtained from this reflector in the horizontal and vertical plane;

Figs. 10 to 12 inclusive are sectional views showing further modifications; and

Figure 13 is an enlarged view illustrating the path of the light rays.

The reflector according to Fig. 1 is intended to concentrate the light parallel to the axis of revolution AA of the surface a. composing it. This surface or instead of being parabolic as is the usual case with reflectors, as shown at a. can be formed to follow a more concentrated me- The exterior surface of the glass is silvered at M and provided with prisms c following the parallels of the surface so that a ray such as art should be sent back after refraction on the smooth interior surface, reflection on exterior prisms and further refraction on the interior surfaces, in a direction (1 parallel to the axis A-A and making with the normal, at the incident surface, an angle of reflection r greater than the incident angle 2'. A reflector according to the present invention enables one to obtain the same result as with a parabolic reflector a. producing reflection in direction d'1. It will particularly be noted that for the same useful light flux the diameter of the reflector according to the invention will be smaller than that of a reflector with a parabolic profile.

Reflectors according to Figs. 2 and 6 are intended more particularly to light corridors or elongated passages, that is to say, so that in sectors 44 Fig. 6, perpendicular to the axis of the corridor the light rays should be reflected in the direction more nearly approaching the vertical than for sectors l-1 corresponding to the axis of the corridors. For sectors 2 and 3 the reflection should be in the intermediate directions. In other words, the reflector should be less and less extensive according as one passes from zone 1 to zone 4. To this end zone 1 remains smoothand the form of the reflector will be such as to produce an extensive distribution. Parallel prisms will be formed in zones 2, 3, and 4 and the angles of these prisms Will increase from zone 2 to zone 4. Zones 4, which are nearest to the division line, are the ones which give the beam the greatest concentration. With reflectors of parallel surfaces such a distribution could not be obtained except with an asymmetric surf ace.

Figs. 7 to 9 show a reflector forshow cases. The reflector is a surface of revolution around axis B-B. That axis is orientated so as to illuminate the upper part of the back of the show case and the profile of the reflector has been chosen so as to hide the filament from the observer. With this orientation of the axis, if the reflector has parallel surfaces, the portion opposite the glass e 1100 would throw rays in a direction such as ff1 following an angle of reflection 1' equal to the angle of incidence i; the luminous flux corresponding will therefore be lost so far as illuminating objects in the show case is concerned. By adding @195 prisms C on the convenient part of the reflector and on the side opposite to the glass in the show case, rays such as of are sent back in direction ff parallel to the plane of the glass and are useful for lighting. One thus obtains in the plane 110 of Fig. 7 the diagrammatic curve of distribution Fig. 8, and by also prolonging the prisms on a portion of the circumference beyond 180, thus preventing the lateral rays from being too divergent in a vertical plane perpendicular to Fig. 7, obtains the curve of distribution represented by Fig. 9.

Fig. 10 shows in section, a reflector similar to Fig. 1 but with annular refracting prisms on the inner surface and silvering or other reflecting means on the outer surface. As in Fig. l a light ray from the light center 0 and incident at d is reflected in the direction d. If the annular refracting prisms were not used the light ray would be reflected in the direction d". In the latter case the angle of incidence i with reference to the reflector contour would be equal to the angle of reflection T, but by means of the annular refracting prisms the angle of reflection is increased to the value r.

Fig. 11 shows in section, a reflector similar to Fig. 10 but with the annular prisms on both surfaces. By this means more difference can be obtained between i and r while using the same size prisms as in Fig. 10, or the same difference can be obtained with shallower prisms.

Fig. 12 shows, one half in section and one half in front view, a reflector using radial prisms on the outer surface as the reflecting means and annular prisms on the outer surface as the means for obtaining an angle of reflection r differing from the angle of incidence i, with reference to the normal to the contour of the reflector. In this case the annular prisms must be reasonably large in order to provide sufficient surface on which to place the reflecting prisms.

Fig. 13 illustrates, at an enlarged scale, the path of a light ray in a typical prism, it being assumed that the ray is in the radial plane of the surface of revolution of the glass. The incident ray is indicated at 10. It strikes the inner surface of the glass at 11 with an angle of incidence 12 with the normal 13, and is refracted toward this normal as indicated at 14. The ray passes through the glass and strikes the rear surface of the glass at 15. Owing to the presence of the silvering M, (or the radial reflecting prisms of Fig. 12) it is reflected as indicated at 16, the angles 17 and 18 being equal. The ray 16 then passes through the clear surface of the glass as indicated at 19, making an angle 20 to the normal which differs from the angle 12 of the incident ray 10. The silvering of the outer surface insures the total reflection of the ray 16 instead of allowing it to emerge as indicated in dotted lines at 21. Since the angle of incidence 17 is less than the critical angle (approximately 413), the mirroring eliminates this refractive transmission of light which would occur were this surface of the glass clear.

It is obvious that the invention may be embodied in many forms and constructions, and I wish it to be understood that the particular forms shown are but a few of the many forms. Various modifications and changes being possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

1. A luminair comprising a light source, a reflector of transparent material placed about the light source and having its outer surface coated with light reflecting material, the reflector carrying annular prisms and being divided into longitudinal zones separated by planes passing through the axis, two of the zones directly opposite each other carrying no annular prisms, the prisms of the zones situate ninety degrees from the plain surfaced zones being of greatest depth to give the light beam the greatest concentration and a two-way asymmetric distribution.

2. A luminair as set forth in claim 1, wherein the prisms of each longitudinal zone extend transversely thereof and parallel to each other.

3. A luminair as set forth in claim 1, wherein the longitudinal zones next adjacent the plain surfaced zones carry shallow prisms and the next adjacent to these carry deeper prisms, etc., so that the zones situate ninety degrees from the plain surfaced zones carry the deepest prisms and a two-way asymmetric distribution is obtained. 4. A luminair as set forth in claim 1, wherein the longitudinal zones to either side of the plain surfaced zones carry parallel transverse prisms in an arrangement that the angles thereof will increase progressively from the zones next adjacent the plain surfaced zones to zones substantially midway between the latter, the prisms in each zone being of substantially uniform angular formation.

5. A luminair comprising a light source, a transparent reflector form placed about the light source and carrying external reflecting means,

the reflector form being divided into longitudinal zones separated by planes passing through the axis, groups of the zones carrying annular prisms and separated by zones free of annular prisms whereby the light reflected by the prism carry- 2' ing zones is more concentrated than the light reflected by the zones free of annular prisms and an asymmetric distribution of reflected light is obtained.

6. A luminair as set forth in claim 5, wherein the prisms of each prism carrying zone group are of varying depth, being shallowest adjacent the zones free of annular prisms and deepest at the mid zones thereof to intensify the light concentration.

7. A luminair as set forth in claim 5, wherein the external reflecting means is in the form of radial prisms.

8. A luminair as set forth in claim 5, wherein the external reflecting means comprises a reflecting coating on the outer surface of the reflector form.

MAURICE EXELMANS. 

